JPS59179127A - Separation of oxygen and nitrogen from gaseous mixture under condition of low temperature and low pressure - Google Patents

Abstract

PURPOSE:To separate efficiently N2 and O2 from a gaseous mixture under the condition of low temp. and low pressure by using at least two adsorbing towers packed with a mineralozical name, sodium faujasite represented by Na-X. CONSTITUTION:Air compressed to 1.05-3 ata by a compressor 2 is introduced to an adsorbing tower 8 via a passage 6. N2 in the compressed air is removed by a N2 adsorbent 9 and the oxygen concentration is increased as the air is sent to the latter part of the tower. Later the compressed air is recovered as a product O2 via a product O2 tank 13. Since said tower 8' is evacuated by a vacuum pump 18 connected thereto, and N2 adsorbed by the adsorbent 9' in the adsorbing tower 8' is desorbed easily by a part of the product O2, the adsorbent is regenerated for a short time. When the adsorbent 9 in said tower 8 is saturated, and regeneration is ended by desorption of N2 from N2 adsorbent in said tower 8, the flow passage 6 of entering air is switched to another passage 6'. By repeating alternately above-mentioned method, the product O2 can be recovered continuously.

Description

DETAILED DESCRIPTION OF THE INVENTION 02+ using a N2 adsorbent that selectively adsorbs N2 from gases 02+ from a mixed gas mainly composed of N2.

The present invention relates to a method for separating N2.

02, N. from air using N2 adsorbent. The adsorption separation method has the advantage that the equipment is small and simple and requires almost no maintenance, which is similar to unmanned operation, so the O2 production amount is 10 to 3 ρ0.
In recent years, the use of small and medium-sized devices such as ON77m'-02b has been increasing, and replacement of cases in which liquid acid produced in cryogenic separation devices is transported and used is progressing.

To give a general overview of this equipment, the equipment is composed of an air compressor, two or more N2 adsorption towers, and in some cases a vacuum pump. In this device, when compressed air is sent to one tower, N2 in the air is adsorbed and removed by the packed N2 adsorbent, and the remaining high pressure 02 flows out to the rear of the adsorption tower and is recovered. On the other hand, in other towers, the adsorbed N2 is released under reduced pressure conditions (sometimes a part of the product O2 is flowed in a countercurrent, or a method of powerfully removing N2 with a vacuum pump is used) for regeneration. This is repeated alternately to continuously separate 02+N2.

A typical adhesive for the N2r1 packed in the adsorption tower mentioned above is Na, which was commercialized by Union Carbide.
- 60-70 qbca exchanger of type A zeolite,
02, which selectively adsorbs N2 from the N2 component mixed gas, and the co-adsorption of 02 under air conditions is
Estimated to be less than 10% of adsorption.

02 due to this adsorption. As mentioned above, the N2 separation equipment is advantageous in the medium/J% type region, but it is necessary to use the 07
The power consumption is higher than the 0.45 Kwh of 02, which is produced by large-capacity cryogenic separation method.

In addition, there is little economy of scale for increasing equipment capacity, and 3
, 0OON-102/h or more, it is said that it cannot compete with the cryogenic separation method.

Therefore, various methods of improving these drawbacks can be considered, but when describing the method of improvement in relation to the present invention, the following obstacles usually appear.

First, in order to reduce power consumption, it is possible to lower the blowing pressure and perform the adsorption operation at low pressure, but since the amount of N2 adsorption decreases almost in proportion to the pressure, the capacity of the device increases significantly. Next, in order to increase the amount of adsorption, it is possible to perform the adsorption operation under low temperature conditions, but in this case, although the amount of N2 adsorbed increases, the adsorption/desorption rate will decrease significantly, so The concentration of product 02 is actually lower than that at room temperature. Also, as the temperature decreases, 0 during N2 adsorption
Since the amount of 2 co-adsorption increases, the power consumption rate gradually increases.

Therefore, the inventors of the present invention have developed a low-temperature solution that improves the above-mentioned drawbacks.

In the process of conducting intensive research and experiments on a high-performance separation method for 02 + NZ under low-pressure adsorption conditions, we discovered that mineral-based sodium faugiasite, represented by Na-X type zeolite, can adsorb N2 under low-temperature, low-pressure adsorption conditions. We have completed the present invention by discovering that as the amount increases, it is possible to maintain N2e and deposition rate within a practical range, and the decrease in N2 adsorption selectivity is small.

In other words, the present invention provides at least two adsorption towers filled with the mineral sodium faujasite represented by Na-X, at a temperature below room temperature, at a temperature above atmospheric pressure. 3aia or less, the nitrogen contained in the mixed gas is flowed into an adsorption tower to selectively adsorb it, and high-purity oxygen or oxygen-enriched gas is flowed out from the outlet of the adsorption tower, while the adsorption tower that has adsorbed nitrogen is .08a ta
The present invention proposes a method for separating oxygen and nitrogen from a mixed gas under low temperature and low pressure conditions, which is characterized by reducing the pressure to below 0.5 ata and regenerating it.

The method of the present invention will be explained in detail below with reference to Examples.

EXAMPLE In order to demonstrate the effectiveness of the present invention, an attempt was made to separate Na-X, etc. from air using an air separation apparatus shown in FIG. 1 using an IJ umfaujasite-based N2 adsorbent.

The details of the implementation will be explained below based on FIG.

Air pressurized to 105 to 3 ata by the compressor 2 through the inlet side line 1 enters the dehumidifying and dehumidifying CO2 tower 4 trap from the flow path 3, and becomes extremely clean pressurized air. The valve 5 installed downstream of the flow path 3' is open, and clean pressurized air enters the adsorption tower 8 through the flow path 6 and the open valve 7. The pressurized air that has entered the adsorption tower 8 has N2 adsorbed and removed by the N2 adsorbent 9, and its temperature increases by 029 degrees as it goes toward the rear. After this, pressurized air is supplied to the open valves 10, 11, 12 and the product 02 tank 13 inserted between the valves 11 and 12.
It is collected as product 02 through the process. On the other hand, a part of the product 02 is depressurized by the pressure reducing valve 15 located in the middle of the flow path 14,
It enters the adsorption column 8' through the open valve 10'. The adsorption tower 8° is depressurized and drawn by the vacuum pump 18 connected through the open valve 16 and flow path 17, and therefore the adsorption tower 8'' is in a negative pressure state with a part of the product 02 in the opposite direction to the air flow. The N2 adsorbed on the adsorbent 9 in the adsorption tower 8° is easily desorbed and the adsorbent 91 is regenerated in a short time.The N2 adsorbent 9 in the adsorption tower 8 is saturated; 8
When N2 leaves the N2 adsorbent 9' and reaches adulthood,
By switching the inlet air flow path 6 to 6' and performing the methods described so far alternately, the product 02 can be continuously recovered. In addition,
A heat exchanger 19 is used to exchange heat between the clean pressurized air line 3°7 at the inlet and the gas line 17 whose main component is N2. The heat exchanger 22 also enables heat exchange between the two.

Also, since a compression refrigerator 20 is installed in the flow path 3',
The adsorption towers 8 and 8" are cooled and set to low temperature conditions in a very efficient manner. When switching the adsorption towers, simply switching from flow path 6 to 6" (or vice versa) is enough. In order to prevent the inlet air from blowing out due to the pressure increase immediately after, and to minimize the release of the 02 remaining at the rear of the adsorption tower and the pressurized air at the front to the outside of the system, first, the pulp 1
Adsorption tower 8 immediately after adsorption with 0, 15, and 10' fully open.
A portion of the remaining 02 at the rear of is transferred to the adsorption tower 8° immediately after regeneration.

At this time, the pressure of the adsorption tower 8 is Po(ata), and the pressure of the adsorption tower 8 is the product o2 tank 1 with the pulp 10° and 11° open.
3 and the adsorption tower are equalized, and the adsorption tower 8 is brought to an even higher pressure. Fill with 2. Pressure P2 when equalizing pressure with product 02 tank 13
aia) is the dead volume of the adsorption tower 8,8° (the volume of the space not occupied by the adsorbent in the adsorption tower), V, (Z), product 0
Assuming that the capacity of the 2 tanks is V2 (t) and the pressure of the product O2 tank 13 before pressure equalization is approximately equal to P6 (ata), it will be equalized, and the PH (ata) when simply switching the tower will be P.

Compared to the rapid increase in pressure to (ara), the above operation P1
Po ten P.

(ata), -2-(ata), P2(ata), P
Since the pressure is gradually increased to G (a ta ), the remaining 02,
Measures can be taken to minimize the release of high-pressure air outside the system.

Air separation was carried out using the air separation apparatus shown in FIG. 1 using the above operating method. The operating specifications of the device are shown in Table 1.

Table 1 Adsorption device specifications 021N2 was separated from air under the operating conditions shown in Table 1.

The results are summarized in Figure 2 and below. From Figure 2 below, the sodium faujasite adsorbent (hereinafter referred to as Na-
Pressure swing from the air due to
60-7 of conventional Na-A type zeolite for N2 adsorption separation
The main improvements over air separation using a 0% Ca exchanger (hereinafter referred to as Ca2A-Na, /1-A) will be explained.

Figure 2 is a graph showing the relationship between adsorption pressure and power consumption. In Figure 2, the horizontal axis is the adsorption pressure Poata, and the vertical axis is 1Nyl? /h is the power consumption (KW) required to manufacture 02. Na-X and Ca2/ as adsorbents
/3- Using Na%-A, temperature 20t, desorption pressure PI = 0.2ata, column internal cylinder speed TJ = 0
．． The power consumption at 0 mark was investigated when the adsorption tower pressure was changed from 15 to 4.5 ata with the setting at 8mH EC (outlet standard). Shown is Na%-A.

As can be seen from Figure 2, conventionally Ca2A-Na
When Na-X, which was thought to be inferior to I/l-A, was investigated in detail, it became Ca2A-Na%-A at an adsorption pressure of 3 ata or less.
In contrast, we have discovered an extremely useful fact that allows oxygen to be separated from air with a smaller power unit. This can be said to be a completely new fact since Na-X has not been used in any conventional air separation method using a N2 adsorbent that has been put into practical use, and it has not been described in any conventional literature.

Next, the adsorption pressure P o is the region where the above effectiveness holds true.
-1,5a ta + empty cylinder speed U = 0.8cm7 s
ec, Ca2A-N8%-A as adsorbent with operating conditions set at temperature 20 °C.

The desorption pressure P+ for each of Na-X is 01 to 0.5a.
The power consumption was measured by changing up to ta, and the results are shown in Figure 3. FIG. 3 is a graph showing the relationship between desorption pressure and power consumption. In Fig. 3, the horizontal axis is the desorption pressure pl (aia
) + The vertical axis shows the power consumption rate during production of 021 Nm'/h. In the figure, mark 0 is Na-X, mark e is Ca, /3-N
a Shown for VA-A. No specific phenomenon was found related to desorption pressure force! , 02 production power consumption by cryogenic separation method is 0.45-0.6KWh I N
m5-02, and the power unit for separation with the current equipment using N2 adsorbent is 0.7KWh/N? ? ＋”−
From the fact that the lower limit is around 0.02 and from FIG. 3, the practical desorption pressure is in the range of Q, Q8 ata to Q, 5 ata, and particularly preferably around 0.1 to 0.3 ata. Next, the adsorption tower was brought to a cooling condition and adsorption separation under low temperature conditions was attempted. This is because the adsorption amount generally increases when the temperature is set to low temperature conditions, so the breakthrough zone during adsorption is reduced, and it was expected that the device would be more compact and the separation efficiency would be improved.

Other operating conditions are adsorption pressure 1.5 ata + regeneration pressure 0.2 ata, cylinder velocity IJ = 0.8 cT.
n/sec and gradually lowered the temperature from room temperature to 021 N? ? +”/ 11 The power consumption rate during manufacturing was determined. Figure 4 is a graph showing the relationship between operating temperature and power consumption rate. In Figure 4, the horizontal axis shows temperature and the vertical axis shows power consumption rate. The 0 mark is for Na-X, the e mark is for Ca2A-
It is shown for N8%-A. As can be seen from Figure 4, in Ca2A-NaVA-A, the power consumption rate increases as the temperature decreases, whereas in Na-X, the power consumption rate continues to decrease as the temperature decreases. Ta. -60℃
We investigated the power consumption of Na-X in the previous range, but no particular problems were found regarding adsorption and separation of air. Furthermore, according to the isobaric data of Na-X in the component system, -1,00℃
However, its effectiveness is not lost. However, a temperature lower than that is not preferable because the co-adsorption of 02 during N2 adsorption cannot be ignored.

Regarding the cooling means, there are no particular problems in this temperature range, and the cooling technology of cryogenic separators can be commonly used.

Significant improvement in performance of Na-X and Ca2A in low temperature region
The incompatibility of -Na l/l-A is also reflected in the 02 concentration at the outlet of the adsorption tower. Figure 5 is a graph showing the relationship between temperature and O2 concentration at the outlet of the adsorption tower. -N8%-A is shown.

The operating conditions are adsorption pressure Po-1,5a ta + desorption pressure P+ = 0.2ata, cylinder speed LJ = 0.4-
The temperature was set at 0.8 on 7 sec, and the temperature was lowered to perform adsorption separation. The curve in FIG. 5 shows the case where U=O, Sα8 to c. As can be seen from Figure 5, Ca
In 2A-Na V3A, the 02 concentration at the outlet of the adsorption tower hardly increases even in the low temperature range, whereas in Na-X, the 02 concentration increases rapidly as the temperature decreases. Furthermore, when the cylinder velocity is 0.4 crn/sec and the temperature is -30°C, 0
The 02 concentration reached 96% (residual gas argon) exceeding the theoretical upper limit of air separation by N2 adsorbent, 945%. This has led to a new method for producing high-purity 02 that can also remove argon by using Na-X in this temperature range.

Furthermore, the fact that the N2 adsorption performance has been improved on the low-temperature side means that the problem of lowering the temperature inside the column due to scale-up is considerably alleviated.

What has been described above is mainly related to power costs and 02 purity, but next we will discuss items related to initial equipment costs. Operating conditions in Figure 5, namely adsorption pressure Po=1.5
aLa, desorption pressure P+=0.2ata, cylinder velocity U
The amount of adsorbent required for producing IN-02 per hour at a rate of 0.8 sub/sec is shown in FIG. Figure 6 is a graph showing the relationship between temperature and the amount of adsorbent mentioned above, in which the horizontal axis is the temperature and the vertical axis is the adsorbent weight [K7] required to produce 1-02 per hour. Yes, 0 marks are for Na-X,
- Marks indicate Ca2/3-Na and A-A.

As can be seen from Figure 6, K Ca 2A-Na, 73-A
Even if the weight of the adsorbent is low, it is about 10% of the weight of the adsorbent at room temperature.
In contrast, with Na-X, it is possible to save about 45% at -30°G, which is extremely effective in reducing the amount of adsorbent, which accounts for a considerable portion of the equipment cost. As described above in detail, according to the present invention, the mineral name sodium faujasite represented by Na-X is used, the adsorption process pressure is 3 ata or less, and the desorption process pressure is 0.08 to 0.
．． If pressure swing type adsorption separation of a mixed gas, for example, air, is carried out under a pressure region of 5 ata and using a temperature range below room temperature, conventionally, the hourly INtt? The power unit required to produce 02 is 0.45 to 0.6 KW using the cold separation method, while 0.7 KW or more is required using the current adsorption separation method.
The amount of adsorbent used can be reduced to 55% of the current adsorbent method.

As explained in detail above, the present invention proposes a method for separating oxygen and nitrogen from a mixed gas that requires less power consumption and less adsorbent than conventional adsorbent methods, and is very useful industrially. It is.

[Brief explanation of drawings]

Figure 1 is an illustration of an air separation device used to carry out the separation method of the present invention, Figure 2 is a graph showing the relationship between adsorption pressure and power consumption, and Figure 3 is a graph showing the relationship between adsorption pressure and power consumption. Figure 4 is a graph showing the relationship between temperature and power consumption, Figure 5 is a graph showing the relationship between temperature and O2 concentration at the outlet of the adsorption tower, and Figure 6 is a graph showing the relationship between temperature and I Nn1''. -o
2/h is a graph showing the relationship with the adsorbent required to produce 2/h. 2...Compressor, 4...Dehumidification/dehumidification CO2 tower, 8...Adsorption tower, 13...Product 02 tank, 18...Vacuum pump, 2o...Compression refrigerator No. 270 Warm Banai force Po (, atal Deinking pressure Pt (atal 4th former 5th M degree [0C1

Claims (1)

[Claims] In at least 2 adsorption towers filled with the mineral name sodium faujasite represented by Na-X, a mixed gas containing oxygen and nitrogen as main components is heated to a pressure above atmospheric pressure and below 3 ata at a temperature below room temperature. The nitrogen contained in the mixed gas is selectively adsorbed by flowing into the adsorption tower, and high-purity oxygen or oxygen-enriched gas is flowed out from the outlet of the adsorption tower, while the adsorption tower that has adsorbed nitrogen is heated to 0.08 alB or more. A method for separating oxygen and nitrogen from a mixed gas under low temperature and low pressure conditions, which comprises regenerating by reducing the pressure to 0.5 ata or less.